There was more than a little disbelief when the Arizona Cardinals went to Gillette Stadium and beat the New England Patriots 20-18 last Sunday.

The Pats were a 13.5-point favorite, and had won ten straight home openers, so something extraordinary had to have taken place for the Cardinals to win, right?

Arizona defensive coordinator Ray Horton shared what he thought was a big difference in the game during Doug and Wolf's show on Arizona Sports 620 Tuesday.

"We knew that whenever [Aaron] Hernandez was in tight, it was going to be a run, so we had a run check. But when he got hurt, it screwed that up because they went to three wide receivers. What they did, and we figured out real quick was, whenever Tom Brady was under the center, they were going to run the ball and whenever he was in the shotgun, they were going to pass the ball," Horton said. "We told our players 'hey, make the run check if Tom Brady's under the center. If he's in the gun, go to the pass check.'

Listen: Ray Horton, Arizona Cardinals Defensive Coordinator

Ray Horton talks about the game plan they had against Tom Brady and the New England Patriots. Plus, he discusses preparing for Michael Vick and the Eagles. And, what made the Cardinals defense so effective against the Patriots?

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"They handled it beautifully, and so we had dual calls that basically what we were telling them is we know when they're going to run and pass, so our players put us in the best position to win the game and they did a flawless job of managing the game of getting inside New England's head."

Wow. Could it be that simple? According to the NFL Game Summary, the Patriots ran 47 plays out of the shotgun formation. Of those 47, 39 were passes, so Horton wasn't exactly 100% on, but there was certainly a tendency for New England to throw out of that formation.

Whatever Horton devised worked. It was only the second time in a decade that a Brady-led offense scored just one touchdown against an opponent.